dipole

1. Physics. A pair of electric charges or magnetic poles, of equal magnitude but of opposite sign or polarity, separated by a small distance.
2. Chemistry. A molecule having two such charges or poles.
3. Electronics. An antenna, usually fed from the center, consisting of two equal rods extending outward in a straight line.

1. a molecule having charges of equal and opposite sign.
2. a pair of electric charges or magnetic poles separated by a short distance.

The noun has 2 meanings:

Meaning #1: a pair of equal and opposite electric charges or magnetic poles separated by a small distance

Meaning #2: an aerial half a wavelength long consisting of two rods connected to a transmission line at the center
  Synonym: dipole antenna